Two-motion selective switch



Feb. 27, 1951 w. R. ROSE TWO-MOTION SELECTIVE SWITCH Filed Sept 9, 1948111,11, Illlt FFF F 7/r/llfllI/l/vllfllllllflllrillllll 'llllIf'l/ll INVEN TOR.

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Patented F eb. 27, l951 2,543,671 TWO-MOTION SELECTIVE SWITCH WilliamRobert Rose, Coventry, England, assignor to The General ElectricCompany, Limited,

London, England Application September 9; 1948, Serial No. 48,421 InGreat Britain September 22, 1947 12 Claims. (01.179-2752) This inventionrelates to electro-magnetic step-by-step switches of the two motion typesuch as are used in telephone systems.

It is an object of our invention to provide a switch of the characterdescribed having improved structural features which enhance itsefficiency, improve its accuracy of selection and facilitate itsassembly.

In general, the improved structure constitutes a fixed shaft and a pairof concentrically disposed hollow cylindrical shafts mounted on thefixed shaft. One of the hollow shafts is arranged to be lifted by avertical stepping magnet while it slides over the other hollow shaft. Atthe end of such vertical movement, the other hollow shaft is rotated onthe fixed shaft by a rotary magnet, the other hollow shaft carrying withit the first hollow shaft to which switch wipers are fastened.

It is a more specific object of our invention to provide a shaftassembly in which free movement between the two hollow shafts other thanthat desired, is reduced to a minimum. This enables accurate positioning.of the wipers on the contact banks to be effected.

Another specific object of our invention is a method of fixing thewipers to the shaft assembly, in such a manner that the wipers areaccurately located thereon, are easily removable therefrom, and do notexert any distorting force.

Reference should now be made to the accompanying drawing in which Figure1 is a sectionalised view of a switch shaft assembly according to ourinvention, Figure 2 is a View of part of the shaft showing theattachment of the wipers, Figure 3 another view of the shaft assemblyshowing the method of locating one of the hollow, shafts relative to theother shaft, and Figure 4 is a wiper bracket assembly. It should benoted that the horizontal dimensions of Figure 1 have been increasedrelative to the vertical dimensions, in order to show the constructionof the assembly more clearly.

In the figures it will be seen that the switch shaft assembly comprisesa first fixed shaft l which is of solid construction. This shaft islocated at its lower end by a hole in part of the switch framework 2 inwhich the shaft is a push fit. At its upper end, the shaft is providedwith several conical depressions and a square shank 3, the shaft passingthrough another hole in another part of the framework 2 in which it isagain an easy push fit. The depressions engage with a plunger A which isurged towards the shaft by a coil spring 5 compressed Rotation of theshaft by the shank 3 causes the plunger 4 to move in and out of thedepressions on the shaft, which is held firmly every time the plungerengages with a depression. The purpose of this arrangement will bedescribed later.

A second shaft 7 of the switch is reamed to be a smooth rotating fit onthe shaft l, and is located so that it may rotate but not slide thereonby the collar 8. This collar is fixed to the shaft 1 by screws (notshown), and the collar may also act as a cam to operate rotary offnormalor other springsets. The shaft 7 is provided with a rotar ratchet 9,which is driven when the switch is in use by a rotary magnet and pawl,the latter of which engages with the ratchet.

A third shaft is of composite character and consists primarily of aratchet body l0 fastened as by soldering to a wiper carrier II, thelatter being in the form of a hollow cylinder provided on the outsidewith webs l2. The ratchet member ID is located on the shaft 1 by meansof a bearing l 3 fixed to the member ID, and the latter is provided withthe usual frustoconical teeth [4. These teeth extend sufficiently fararound the shaft to enable it to be held in any position to which it isstepped by the vertical magnet, when the whole assembly is rotated. Thevertical ratchet may engage with the teeth shown or alternatively andpreferably the said teeth may be cut away opposite the point where thevertical pawl engages during vertical stepping, being replaced by astrip of teeth made of a harder material such as steel oraluminiumbronze, this construction reducing the wear on the teeth whilstenabling the member In to be made of softer material such as brass whichis more easily machined.

By the means outlined it will be seen that a shaft assembly is providedin which the minimum possible shake of the various parts on each otherhas been ensured. It is also necessary that when the second and thirdshafts are rotated together under the influence of the rotary magnet,substantially no free rotary movement of the third shaft takes placerelative to the second. To promote this action the second shaft member 1is provided with a key 22. This key passes through the gap which is leftin the member If] which is cut away at 23. On the fiat face left by thisoperation, two steel strips 24, 25-are mounted. The first strip 24 isfixed by screws in position in a jig so that its inner vertical face isexactly parallel with the axis of the assembly. The shaft 1 is nowinserted through the bearing l3, and one edge of the key put against themember 24. The strip 25, which is provided with elongated fixing holes,is brought against the other edge of the key and screwed in position soas to provide the minimum possible amount of free rotational movement ofthe shaft 1 relative to the outer shaft. Thus the latter may slidefreely over the former, but not rotate relatively to it.

In view of the accuracy possible, and, in fact, necessary between thevarious shafts, it is advisable to ensure that the method of fixing thewipers to the cylinder H is such that substantially no distortion of thewhole assembly is caused. We ensure this by providing the cylinder withwebs l2 disposed 180 apart. These webs may be continuous or, as shown,portions may be cut away where desired. Each wiper assembly consists ofa body member 26 having a curved inner surface of radius substantiallyequal to the outer radius of the cylinder H. This bod member is fittedat each end with a small plate 2! fixable to the body member by a screw28. Each wiper may be made with a small cylinder shaft or other meansfor attaching the said wiper to the body. When a wiper assembly is to befixed in position the screws 28 are slackened off and the wiper bodyplaced on the shaft and slid in position, the body passing on one sideof the webs and the fixing plates 21 on the other side. When the screws28 are tightened the webs are gripped between the plates and the body,holding the whole assembly firmly in position without distortion of thecylinder H, such as may be caused for example by its encirclement by aband which is tightened to hold wipers in position. Separate adjustmentof the wiper tips relative to the contact bank is provided by meansadopted to fix the wipers to the carrier.

To ensure return of the wipers to a normal position i. e. below andoutside the contact bank, after the switch has been rel ased from use,we provide two coil sprin s I1, 29, spring I! is slightly compress d,when the assembly is in the said normal position, between the bearing l5and the bush is but it is not fixed to either of these. The bearing isfixed to the cylinder I I and the bush It to the shaft I so thatvertical movement of the cylinder and wipers compresses the spring l'l.When the rotary magnet rotates the second shaft 1, the spring is woundup. The lower end of this spring is fixed to the bush !6 and the upperend to the shaft 1; the spring is also given an initial turn or two byrotation of the shaft l by the shank 3, the plunger 4 preventingbackward rotation of the shaft I. Release in first a rotary and then avertical direction is ensured by engagement of a guide (not shown)mounted on the framework and engaging with the frustoconical teeth ofthe vertical ratchet.

It will be seen from the foregoing description t1 at a wiper shaftassembly has been provided capable of relatively easy construction,having the minimum amount of unwanted relative movement between itsparts, easy adjustment of the various tolerances, and minimum distortionby the various processes of assembly.

I claim: I

l. A two-coordinate switch of the type used in telephone systems, saidswitch comprising a framework having two spaced elements, a first shaftwith its ends in said elements and spanning the space therebetween,means to fixedly secure said first shaft to said framework, a secondshaft, said second shaft being hollow and coaxial with said first shaft,said first shaft extending through said second shaft and projectingbeyond the ends thereof, means to mount said second shaft on said firstshaft for rotational movement with respect thereto, said mounting meansincluding means to prevent axial movement of said second shaft relativeto said first shaft, a third shaft, said third shaft being hollow andcoaxial with said first two two shafts, said second shaft beingpartially disposed within said third shaft, means to mount said thirdshaft on said second shaft for axial movement with respect thereto, saidlast named mounting means including means to prevent rotation of saidthird shaft relative to said second shaft, and a wiper assembly attachedto the third shaft.

2. A switch as set forth in claim 1 wherein the first shaft is fixed toone of the framework elements at one end thereof and is supported by theother framework element at the other end thereof, and wherein means isincluded to apply a rotary stepping force to the second shaft at a pointnear the framework element whereat an end of the first shaft is secured.

3. A switch as set forth in claim 1 wherein the second shaft is providedwith a rotary ratchet of cylindrical form and the third shaft isprovided with a vertical ratchet formed as a superimposed series oftruncated cones.

4. A switch as set forth in claim 1 wherein the means to preventrotation of the third shaft relative to the second shaft comprises a keyon the second shaft and an adjustable slot on the third shaft, saidadjustable slot being formed by a hardened steel strip carried by thethird shaft with an edge thereof parallel to the axes of the shafts, asecond hardened steep strip, and means to mount said second strip on thethird shaft, said last named means permitting transverse adjustment ofan edge of the second strip relative to the mentioned edge of the firststrip, said edges of the strip being adjacent opposite longitudinalsides of the key.

5. A switch as set forth in claim 1 wherein the third shaft is providedwith a pair of radially extending webs, each wiper assembly including abody having a pair of clamping means, one of which detachably engagesone of the webs and the other of which detachably engages the other web,said body extending between said clamping means.

6. A switch as set forth in claim 1 wherein the third shaft is providedwith a pair of radially extending webs disposed apart about the axis ofsaid shaft, each wiper assembly including a body having a pair ofclamping means, one of which detachably engages one of the webs and theother of which detachably engages the other web, said body extendingbetween said clamping means.

7. A switch as set forth in claim 1 wherein the third shaft has an innerdiameter greater than the outer diameter of the second shaft, whereinthe third shaft extends beyond the second shaft, and wherein the thirdshaft is provided with two bearings carried thereby, one of saidbearings sliding on the second shaft and the other of said bearingssliding on the first shaft.

other coil spring being connected between the first shaft and the secondshaft.

9. A switch as set forth in claim 1 wherein means is provided to restorethe second and third shafts to a normal position, said means comprisingtwo independent coil springs, one of said coil springs being under axialtension between the first and third shafts and the other of said coilsprings being under rotary tension between the first and second shafts.

10. A switch as set forth in claim 1 wherein the third shaft is providedwith a vertical ratchet formed as a superimposed series of truncatedcones, and adapted to be engaged by a vertical stepping pawl when theratchet is in a predetermined angular position with respect to the pawl,the portion of said ratchet engaged by the pawl during vertical steppingbeing made of a material harder than the remainder of the ratchet.

11. A switch as set forth in claim 1 wherein means is provided 'torestore the second shaft to a normal position, said means comprising aspring under rotary tension between the first and second shafts, themeans to fixedly secure the first shaft to the framework including aspring-loaded plunger carried by the framework and disposed to engage adepression in the shaft so that an initial rotary restoring tension canbe imparted to said spring by turning the first shaft.

12. A two co-ordinate switch of the type used in telephone systemscomprising a framework, a first fixed shaft, a second hollow cylindricalshaft, a third hollow cylindrical shaft having a wiper contact assemblyrigidly attached thereto, all of said shafts being coaxial, said firstshaft b; ng secured to said framework at one of its extremities andsupported by it at its other extre'inity, a collar and a first bushsituated at the upper end of said second shaft and between said firstshaft and said second shaft, said collar being situated partially withina circumferential groove in said first shaft, a rotary cylindricalratchet integral with said second shaft, an ad- 'ju'stable width keywaybetween said second shaft and said third shaft comprising two adjustablehard metal strips on said third shaft between {which is situated aspline formed on said second shaft, a vertical ratchet comprising anumber of superimposed truncated cones integral with said third'shaft, afixed collar situated at approximately the mid-point of said first shaftand a second bush fixed to the lower end of said wiper contact assemblycarrying hollow cylindrical I shaft and axially slidable on said firstshaft, an

REFERENCES CITED The following references are of record in the file ofthis patent:

UNITED STATES PATENTS Number Name Date 1,718,449 Aldendorif June 25,1929 Saxby Jan. 21, 1936

